Electrodeless discharge lamp lighting device, light bulb type electrodeless fluorescent lamp and discharge lamp lighting device

ABSTRACT

An electrodeless discharge lamp operating device including an electrodeless discharge lamp  3  and a ballast circuit  4 , wherein the ballast circuit  4  includes: an AC-DC converter  5  for converting a phase-controlled AC voltage into a DC voltage; a DC-AC converter  6  formed so as to intermittently drive the electrodeless discharge lamp  3  due to the existence of an operating period during which a high-frequency voltage is applied to the electrodeless discharge lamp  3  so that the electrodeless discharge lamp  3  is operated, and an extinguishing period during which the generation of the high-frequency voltage is stopped so that the electrodeless discharge lamp  3  is extinguished; and a dimming controller  7  for detecting the turn-on of the phase-controlled AC voltage, for outputting an intermittent command signal that changes the ratio between the operating period and the extinguishing period to the DC-AC converter  6 , and for outputting a signal that maintains an intermittent dimmable operating state even if dimming state is in full illumination.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP03/07235, filed Jun. 6, 2003. This application claims the benefitof 2002-167613, filed Jun. 7, 2002. The disclosure of the aboveapplications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to discharge lamp operating devices andelectrodeless discharge lamp operating devices. In particular, thepresent invention relates to electrodeless self-ballasted fluorescentlamps in which electrodeless fluorescent lamps can be dimmed.

BACKGROUND ART

A fluorescent lamp has been widely used from global environmentalprotection and economic standpoints because it has a higher degree ofefficiency and a longer life as compared with an incandescent lamp. Inrecent years, as an economical light source, an electrodelessself-ballasted fluorescent lamp having no electrode has been attractingmuch attention since its life is several times longer than that of aconventional self-ballasted fluorescent lamp having electrodes, and thedemand for an electrodeless self-ballasted fluorescent lamp is on theincrease.

Furthermore, a self-ballasted fluorescent lamp in which a fluorescentlamp and a ballast circuit therefor are integrally formed is becoming afocus of attention as an energy-saving light source in houses, hotels,restaurants or the like, and is now becoming widespread because theself-ballasted fluorescent lamp can be readily used as it is in place ofan incandescent lamp. In addition to the self-ballasted fluorescent lampof this type having electrodes, the self-ballasted fluorescent lamp ofthis type having no electrode is also under development.

With the widespread use of the self-ballasted fluorescent lamp, as witha dimmable incandescent lamp, the need for dimming of the self-ballastedfluorescent lamp is being created. To be more specific, in houses orhotels, people carry out various daily living activities such as readingor spending a happy time with family, and in order to achieve acomfortable light environment adapted to these daily living activities,a user desires brightness suitable to each situation and seeks afunction that realizes such brightness. Since an incandescent lamp doesnot emit light by discharge, it can be easily dimmed by merely adjustingelectric power supplied thereto. On the other hand, since a fluorescentlamp emits light by discharge, it is difficult to implement a dimmablefluorescent lamp that can be practically used by merely adjustingelectric power supplied thereto like an incandescent lamp.

Lately, in response to a need for a user to change brightness utilizingan already-known incandescent lamp dimmer as with an incandescent lamp,a self-ballasted fluorescent lamp with electrodes, which is connected toan incandescent lamp dimmer and allows dimmable operation, has beendeveloped (see Japanese Unexamined Patent Publication No. 1999-111486,for example). However, the fact is that an electrodeless self-ballastedfluorescent lamp which is dimmable has not yet developed.

The present applicant has already developed an electrodelessself-ballasted fluorescent lamp that is dimmable, and succeeded incompleting such a lamp; however, this lamp still has inadequacies. Forexample, if dimming is carried out from full illumination state so thatluminous flux is reduced, discontinuous luminous flux change occurs,thus making a user feel uncomfortable. Even if a dimmable incandescentlamp is dimmed in such a manner, luminous flux change thereof iscontinuous; therefore, a user who has been using a dimmable incandescentlamp particularly feels very uncomfortable in utilizing a dimmableelectrodeless self-ballasted fluorescent lamp.

The present invention has been made in view of the above-describedproblems, and its main object is to provide an electrodelessself-ballasted fluorescent lamp, an electrodeless discharge lampoperating device and a discharge lamp operating device which suppressthe occurrence of discontinuous luminous flux change.

DISCLOSURE OF THE INVENTION

A first inventive electrodeless discharge lamp operating deviceincludes: an electrodeless discharge lamp; and a ballast circuit forapplying a high-frequency voltage to the electrodeless discharge lamp,wherein the ballast circuit includes: an AC-DC converter for convertinga phase-controlled AC voltage into a DC voltage; a DC-AC converter forconverting the DC voltage into a high-frequency voltage, the DC-ACconverter being formed so as to intermittently drive the electrodelessdischarge lamp due to the existence of an operating period during whichthe high-frequency voltage is applied to the electrodeless dischargelamp so that the electrodeless discharge lamp is operated, and anextinguishing period during which the generation of the high-frequencyvoltage is stopped so that the electrodeless discharge lamp isextinguished; and a dimming controller for detecting the turn-on of thephase-controlled AC voltage, for outputting an intermittent commandsignal that changes the ratio between the operating period and theextinguishing period to the DC-AC converter, and for outputting a signalthat maintains an intermittent dimmable operating state even if dimmingis in full illumination state.

A second inventive electrodeless discharge lamp operating deviceincludes: an electrodeless discharge lamp; and a ballast circuit forapplying a high-frequency voltage to the electrodeless discharge lamp,wherein the ballast circuit includes: an AC-DC converter for convertinga phase-controlled AC voltage into a DC voltage; a DC-AC converter forconverting the DC voltage into a high-frequency voltage; and a dimmingcontroller for outputting an intermittent driving signal to the DC-ACconverter, wherein the dimming controller includes: a circuit forgenerating a sawtooth wave or a triangular wave synchronized with theturn-on of the phase-controlled AC voltage; and a dimming command signalgenerator for generating a dimming command signal, and wherein thedimming controller is formed so as to prevent the dimming command signalfrom exceeding a limiter value set lower than the maximum value of thevoltage variation range of the sawtooth wave or triangular wave.

In one preferred embodiment, the dimming controller has a voltagelimiter, which is connected to the dimming command signal generator, forpreventing the dimming command signal from exceeding the limiter value.

The dimming controller is preferably further formed so as to output asignal for synchronizing the timing of the turn-on with that of theoperation of the lamp intermittently driven by the DC-AC converter.

A third inventive electrodeless discharge lamp operating deviceincludes: an electrodeless discharge lamp; and a ballast circuit forapplying a high-frequency voltage to the electrodeless discharge lamp,wherein the ballast circuit includes: an AC-DC converter for convertinga phase-controlled AC voltage into a DC voltage; a DC-AC converter forconverting the DC voltage into a high-frequency voltage and forintermittently driving the electrodeless discharge lamp; and a dimmingcontroller for detecting the turn-on of the phase-controlled AC voltageand for outputting an intermittent command signal that changes the ratiobetween an operating period and an extinguishing period to the DC-ACconverter, and wherein the dimming controller includes: a circuit forgenerating a sawtooth wave or a triangular wave responsive to theturn-on phase of the waveform of the phase-controlled voltage; a dimmingcommand signal generator for generating a dimming command signalresponsive to the turn-on phase of the waveform of the phase-controlledvoltage; a comparator for comparing the voltage of the sawtooth wave ortriangular wave with that of the dimming command signal and foroutputting the intermittent command signal; and a voltage limiterprovided between the comparator and the dimming command signalgenerator.

In one preferred embodiment, the dimming controller does not output asignal for placing the electrodeless discharge lamp into a continuousoperating state even if dimming state reaches full illumination, andoutputs a signal for placing the electrodeless discharge lamp into anintermittent dimmable operating state even if dimming state is in fullillumination.

In one preferred embodiment, the dimming controller has a sawtooth wavegenerator including a differentiating circuit that includes a capacitorand a resistor, wherein the differentiating circuit is connected to acollector terminal of a transistor for generating a pulse wavesynchronized with the turn-on and turn-off of the phase-controlled ACvoltage, wherein an output terminal of the differentiating circuit isconnected with an anode of a diode while a cathode of the diode isconnected with a base terminal of a transistor for discharge, andwherein a capacitor for charge and discharge is connected between acollector terminal and an emitter terminal of the transistor fordischarge, thus allowing the generation of a sawtooth wave synchronizedwith the turn-on of the phase-controlled AC voltage.

In one preferred embodiment, the phase-controlled AC voltage is anoutput voltage of a dimmer which has been phase-controlled by thedimmer.

An inventive electrodeless self-ballasted fluorescent lamp includes: anelectrodeless fluorescent lamp; a ballast circuit for applying ahigh-frequency voltage to the electrodeless fluorescent lamp; and a lampbase electrically connected to the ballast circuit, wherein theelectrodeless fluorescent lamp, the ballast circuit and the lamp baseare formed as one unit, wherein the ballast circuit includes: an AC-DCconverter for converting a phase-controlled AC voltage into a DCvoltage; a DC-AC converter for converting the DC voltage into ahigh-frequency voltage, the DC-AC converter being formed so as tointermittently drive the electrodeless fluorescent lamp due to theexistence of an operating period during which the high-frequency voltageis applied to the electrodeless fluorescent lamp so that theelectrodeless fluorescent lamp is operated, and an extinguishing periodduring which the generation of the high-frequency voltage is stopped sothat the electrodeless fluorescent lamp is extinguished; and a dimmingcontroller for detecting the turn-on of the phase-controlled AC voltage,for outputting an intermittent command signal that changes the ratiobetween the operating period and the extinguishing period to the DC-ACconverter, and for outputting a signal that maintains an intermittentdimmable operating state even if dimming is in full illumination state.

An inventive discharge lamp operating device includes: a discharge lamp;an AC-DC converter for converting a phase-controlled AC voltage into aDC voltage; a DC-AC converter for converting the DC voltage into ahigh-frequency voltage, the DC-AC converter intermittently driving thedischarge lamp due to the existence of an operating period during whichthe high-frequency voltage is applied to the discharge lamp so that thedischarge lamp is operated, and an extinguishing period during which thegeneration of the high-frequency voltage is stopped so that thedischarge lamp is extinguished; and a dimming controller for detectingthe turn-on of the phase-controlled AC voltage, for outputting anintermittent command signal that changes the ratio between the operatingperiod and the extinguishing period to the DC-AC converter, and foroutputting a signal that maintains an intermittent dimmable operatingstate even if dimming is in full illumination state

The dimming controller is preferably further formed so as to output asignal for synchronizing the timing of the turn-on with that of theoperation of the lamp intermittently driven by the DC-AC converter.

In one preferred embodiment, the discharge lamp has a discharge bulbhaving a recessed portion, and an induction coil is inserted into therecessed portion of the discharge bulb.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the circuit configuration of anelectrodeless discharge lamp operating device (electrodelessself-ballasted fluorescent lamp) according to a first embodiment of thepresent invention.

FIG. 2 is a cross-sectional view schematically showing the structure ofthe electrodeless self-ballasted fluorescent lamp of the firstembodiment.

FIG. 3 illustrates waveform charts showing various waveforms in anintermittent dimmable operating state.

FIG. 4 illustrates waveform charts showing various waveforms in acontinuous operating state.

FIG. 5 illustrates waveform charts for describing the occurrence ofdiscontinuous luminous flux change during darkening from a fullillumination mode.

FIG. 6 is a diagram showing the circuit configuration of a dischargelamp operating device according to a second embodiment of the presentinvention.

FIG. 7 is a diagram showing the circuit configuration of a dischargelamp operating device according to a third embodiment of the presentinvention.

FIG. 8 is a diagram showing the circuit configuration of an asynchronoustype discharge lamp operating device.

FIG. 9 illustrates various waveform charts concerning the discharge lampoperating device shown in FIG. 8.

FIG. 10 illustrates various waveform charts concerning the dischargelamp operating device shown in FIG. 8.

BEST MODE FOR CARRYING-OUT OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. In the following drawings, for simplificationof the description, the same constituting elements having substantiallyidentical functions are identified by the same reference characters. Itshould be noted that the present invention is not limited to thefollowing embodiments.

(Embodiment 1)

FIG. 1 schematically shows the configuration of a discharge lampoperating device (electrodeless discharge lamp operating device)according to a first embodiment of the present invention. And FIG. 2 isa cross-sectional view of the discharge lamp operating device of thepresent embodiment implemented as an electrodeless self-ballastedfluorescent lamp.

The electrodeless self-ballasted fluorescent lamp of the presentembodiment includes: an electrodeless fluorescent lamp 3; a ballastcircuit 4 (circuit board 54) for applying a high-frequency voltage tothe electrodeless fluorescent lamp 3; and a lamp base 56 electricallyconnected to the ballast circuit 4 (circuit board 54). The circuit board54 shown in FIG. 2 is formed with the ballast circuit 4 shown in FIG. 1.Specifically, the circuit board 54 is formed with wirings provided asshown in the ballast circuit 4, and is attached with respective circuitcomponents.

As shown in FIG. 2, in the electrodeless self-ballasted fluorescentlamp, the electrodeless fluorescent lamp 3, the ballast circuit 4(circuit board 54) and the lamp base 56 are formed as one unit. In thisembodiment, the electrodeless fluorescent lamp 3 includes a dischargebulb 17 having a recessed portion 17 a, and an induction coil 16 made upof a core 16 a and a coil 16 b is inserted into the recessed portion 17a. The coil 16 b is electrically connected to the circuit board 54, anda cover 55 for accommodating the circuit board 54 is provided around thecircuit board 54. The lamp base 56 (e.g., E26 type for incandescentlamp) is attached to a lower part of the cover 55, and is electricallyconnected to the circuit board 54. By screwing the lamp base 56 into asocket for an incandescent lamp, the supply of electric power isallowed, and thus the operation of the electrodeless fluorescent lamp 3is enabled. An AC voltage inputted through the lamp base 56 is an ACvoltage that is phase-controlled by, for example, an external phasecontroller (such as a dimmer 2 shown in FIG. 1, typically a dimmer foran incandescent lamp).

The ballast circuit 4 shown in FIG. 1 includes: an AC-DC converter 5 forconverting a phase-controlled AC voltage into a DC voltage; a DC-ACconverter 6 for converting the DC voltage, which has been converted inthe AC-DC converter 5, into a high-frequency voltage; and a dimmingcontroller 7. It should be noted that the AC-DC converter 5, the DC-ACconverter 6 and the dimming controller 7 may be called a converter forsmoothing an AC voltage into a DC voltage, an inverter and a detector(detection means), respectively.

The ballast circuit 4 is connected to a commercial power supply 1 viathe dimmer 2 for carrying out the phase control of a voltage suppliedfrom the commercial power supply 1. Furthermore, the ballast circuit 4operates the electrodeless fluorescent lamp 3 in response to the turn-onof the voltage phase-controlled in the dimmer 2. The commercial powersupply 1 is an AC power supply for 60 Hz and 100V, for example, and thedimmer 2 is connected thereto. The dimmer 2 is one that carries outphase control using a triac, and a commercially available dimmer for anincandescent lamp can be typically used as the dimmer 2.

The AC-DC converter 5 converts the phase-controlled voltage, suppliedfrom the dimmer 2, into a DC voltage. As the AC-DC converter 5, one thatutilizes a diode bridge and a smoothing capacitor, for example, may beused. The DC-AC converter 6 is formed so as to intermittently drive theelectrodeless fluorescent lamp 3 due to the existence of an operatingperiod during which the converted high-frequency voltage is applied tothe electrodeless fluorescent lamp 3 so that the electrodelessfluorescent lamp 3 is operated, and an extinguishing period during whichthe generation of the high-frequency voltage is stopped so that theelectrodeless fluorescent lamp 3 is extinguished.

As shown in FIG. 1, the DC-AC converter 6 of the present embodimentincludes: an oscillator 8; a switching circuit 9; a driving circuit 10;switching elements (MOSFETs 11 and 12); a resonant inductor 13; andresonant capacitors 14 and 15. Specifically, the induction coil 16 isconnected to the resonant capacitor 15 in series, and furthermore, aseries circuit of the induction coil 16 and the resonant capacitor 15 isconnected to the resonant capacitor 14 in parallel. In this embodiment,the electrodeless fluorescent lamp 3 is formed by the induction coil 16and the electrodeless discharge bulb 17. The induction coil 16 is madeup of the ferrite core 17 a and the coil 16 b, and is placed into therecessed portion 16 a of the discharge bulb 17.

The dimming controller 7 is formed so as to detect the turn-on of thephase-controlled AC voltage, and so as to output an intermittent commandsignal for changing the ratio between the operating period andextinguishing period to the DC-AC converter 6 (in particular, theswitching circuit 9). Further, the dimming controller 7 is formed so asto output a signal for maintaining an intermittent dimmable operatingstate even if dimming is in full illumination state. In the presentembodiment, in order to implement the dimming controller 7 formed inthis way, the dimming controller 7 is provided with a voltage limiter25. Furthermore, the dimming controller 7 of the present embodiment isformed so as to output a signal for synchronizing the timing of theturn-on with that of the operation of the electrodeless fluorescent lamp3 intermittently driven by the DC-AC converter 6. In other words, thedimming controller 7 can be called a synchronous type duty modulator.

As shown in FIG. 1, the dimming controller 7 of the present embodimentincludes: a dimming control signal input section A 18; a photo coupler19; a sawtooth wave generator 20; a dimming command signal input sectionB 21; a dimming command signal generator 22; the voltage limiter 25; anda comparator 23 (e.g., a comparator formed using an operationalamplifier). By using the photo coupler 19, the dimming control signalinput section A 18 and the sawtooth wave generator 20 can be insulatedfrom each other; therefore, noise reduction can be achieved, andperformance increase can be attained. A sawtooth wave is generated usingthe dimming control signal input section A 18, to which the voltagephase-controlled by the dimmer 2 is inputted, the photo coupler 19 andthe sawtooth wave generator 20. Alternatively, a triangular wavegenerator may be used instead of the sawtooth wave generator 20.

Furthermore, a dimming command signal is generated using the dimmingcommand signal input section B 21 and the dimming command signalgenerator 22, and then, the sawtooth wave is sent to the non-invertinginput terminal of the comparator 23 while the dimming command signal issent to the inverting input terminal of the comparator 23; thus, fromthe resulting voltage difference, the comparator 23 generates anintermittent dimming signal. Between the comparator 23 and the dimmingcommand signal generator 22, the voltage limiter 25 is provided, and thevoltage limiter 25 prevents the dimming command signal, sent from thedimming command signal generator 22, from exceeding a limiter value setlower than the maximum value of the voltage variation range of thesawtooth wave. By adopting such a configuration, the dimming controller7 of the present embodiment does not output a signal for placing theelectrodeless discharge lamp 3 into a continuous operating state even ifdimming state reaches full illumination, and can output a signal forplacing the electrodeless discharge lamp 3 into the intermittentdimmable operating state even if dimming state is in full illumination.

Hereinafter, the operation of the electrodeless discharge lamp operatingdevice according to the first embodiment will be described.

First, an output voltage from the commercial power supply 1 isphase-controlled in the dimmer 2, and then the phase-controlled ACvoltage is converted into a DC voltage in the AC-DC converter 5.

Next, the driving circuit 10 for the MOSFETs 11 and 12 of the DC-ACconverter 6 is driven in response to an output at a driving frequency f1(Hz) from the oscillator 8. By allowing the two MOSFETs 11 and 12 toalternately turn on and off, the DC voltage smoothed by the AC-DCconverter 5 is converted into a high-frequency voltage.

Subsequently, the high-frequency voltage is applied to a resonantcircuit made up of the resonant inductor 13, the resonant capacitors 14and 15, and the induction coil 16. Due to a current flowing through theinduction coil 16, an AC electromagnetic field is generated within theelectrodeless discharge bulb 17, and an energy supplied by the ACelectromagnetic filed causes excitation of a light-emitting gas (notshown) enclosed within the electrodeless discharge bulb 17, resulting inlight emission. As the light-emitting gas, for example, mercury,krypton, xenon or a gas mixture thereof may be used. Optionally, a gascontaining only a rare gas but no mercury may also be used.

Note that, in that case, the timing of the turn-on of thephase-controlled voltage is detected by the dimming controller 7, andthe turn-on of the intermittent command signal synchronized with theturn-on of the phase-controlled voltage occurs in the dimming controller7 and is transmitted to the switching circuit 9. Over the period duringwhich the intermittent command signal is transmitted to the switchingcircuit 9 (i.e., the on period, or the operating period of theelectrodeless fluorescent lamp 3), the switching circuit is turned on,and the driving circuit 10 for the MOSFETs 11 and 12 is turned on. Tothe contrary, over the period during which the intermittent commandsignal is not transmitted to the switching circuit 9 (i.e., the offperiod, or the extinguishing period of the electrodeless fluorescentlamp 3), the switching circuit 9 is turned off, and the driving circuit10 for the MOSFETs 11 and 12 is turned off. During the on period of theswitching circuit 9, the turning on and turning off of the MOSFETs 11and 12 are alternately repeated with the driving frequency f1 (Hz). Inaccordance with a variation in the conduction period of the voltagephase-controlled by the dimmer 2, the ratio between the on period andoff period of the switching circuit 9, determined by the intermittentcommand signal from the dimming controller 7, is changed, and inaccordance with this change, the ratio between the on period and offperiod of the MOSFETs 11 and 12 (which will be herein called a dutyratio) is varied. That is, the variation in the duty ratio causes achange in an electric energy input to the electrodeless fluorescent lamp3, thus carrying out dimming of the electrodeless fluorescent lamp 3.

Hereinafter, the operation of the dimming controller 7 will be describedin detail with reference to also FIG. 3. FIG. 3 shows the relationshipsamong a phase-controlled voltage a, a turn-on detection signal b, asawtooth wave c, a dimming command signal d, an intermittent commandsignal e, and a light output f, wherein in the five charts, eachhorizontal axis is a time axis, and the time axis serves as a commonmeasure in the respective charts.

The phase-controlled voltage a in FIG. 3 is first inputted to thedimming control signal input section A 18 in the dimming controller 7shown in FIG. 1. Then, the phase-controlled voltage a is full-waverectified in the dimming control signal input section A 18, and issubsequently reduced to a voltage (e.g., 2V) appropriate for the drivingof the photo coupler 19 and applied to the photo coupler 19.

Concurrently with the turn-on of the voltage phase-controlled in thedimmer 2, there occurs the turn-on of the full-wave rectified voltageinputted to the photo coupler 19. Next, after the rise time of the photocoupler 19 (e.g., 20 μs), a light emitting diode incorporated into thephoto coupler 19 emits light.

Due to the light emission of the diode, a pulse wave synchronized withthe turn-on and turn-off of the phase-controlled voltage a is outputtedfrom a transistor that forms a part of the photo coupler 19. Then, dueto the existence of an IC such as a monostable multivibrator, thesawtooth wave generator 20 outputs the turn-on detection signal bsynchronized only with the turn-on of the phase-controlled voltage a byusing, as a trigger input, the turn-on signal from the photo coupler 19.

The turn-on detection signal b is sent to a base terminal of thetransistor, a capacitor connected between an emitter and a collector ofthe transistor is charged and discharged, and the sawtooth wave c isoutputted.

On the other hand, the phase-controlled voltage a is inputted to thedimming control signal input section B 21 of the dimming controller 7shown in FIG. 1, and is half-wave rectified by the dimming controlsignal input section B 21. Then, in the dimming command signal generator22, the half-wave rectified portion of the phase-controlled voltage isintegrated, and thereafter the dimming command signal d is outputted.

The comparator 23 receives, at its non-inverting input terminal andinverting input terminal, the sawtooth wave c and the dimming commandsignal d, respectively, and outputs the intermittent command signal e inaccordance with the potential difference between both the signals.

Thereafter, the intermittent command signal e is transmitted to theswitching circuit 9, and during the on period of the intermittentcommand signal e, the MOSFETs 11 and 12 of the DC-AC converter 6 aredriven with the driving frequency f1 (Hz), thereby obtaining the lightoutput f.

The on state of the intermittent command signal e is maintained untilthe potential of the sawtooth wave c becomes higher than that of thedimming command signal d. Upon inversion of the potential relationship,the intermittent command signal e becomes off, which is transmitted tothe switching circuit 9, and the driving of the MOSFETs 11 and 12 isstopped, thus extinguishing light.

In this manner, the duty of the intermittent command signal e isdetermined by the potential relationship between the potential of thesawtooth wave c and that of the dimming command signal d, andfurthermore, the operation during the on period of the intermittentcommand signal e and the extinguishing during the off period of theintermittent command signal e are repeated, thus enabling intermittentdimming.

In addition, the sawtooth wave generator 20 is set such that a certainpotential is secured even if electrical charges of the capacitor forcharge and discharge are completely discharged. For example, if threediodes, each having a forward voltage of about 0.6V, are connected tothe emitter terminal, the minimum potential of the sawtooth wave cbecomes about 1.8V. Besides, since the charge and discharge are carriedout using, as a trigger, the signal of the turn-on of thephase-controlled voltage, the sawtooth wave maintains a constantwaveform even if the conduction angle of the phase-controlled voltage ischanged. On the other hand, since the half-wave rectified portion of thephase-controlled voltage is integrated, the potential of the dimmingcommand signal d is changed, and if the potential of the dimming commandsignal d becomes equal to or lower than a certain potential (minimumpotential) of the sawtooth wave c, all the intermittent command signalse enter the off period. And at or below a certain conduction angle ofthe phase-controlled voltage (i.e., at or below a conduction angle atwhich the minimum potential of the sawtooth wave c and the potential ofthe dimming command signal d become equal to each other), the driving ofthe MOSFETs 11 and 12 of the DC-AC converter 6 is stopped and thus thelight is extinguished.

Thus, by adjusting the minimum potential of the sawtooth wave c, thedriving of the MOSFETs 11 and 12 of the DC-AC converter 6 can be stoppedand the light can be extinguished at an arbitrary phase level of thephase-controlled voltage from the dimmer.

Hereinafter, with reference to also FIG. 4, description will be madeabout the mechanism of the occurrence of discontinuous luminous fluxchange during dimming (darkening from a full illumination mode). FIG. 4illustrates, in the configuration in which the dimming controller 7 isprovided with no voltage limiter 25, various waveforms during fullillumination in the continuous operating state.

As already shown in FIG. 3, in the intermittent dimmable operatingstate, a non-operating period (light extinction period) exists. On theother hand, as shown in FIG. 4, in the continuous operating state, thenon-operating period (light extinction period) does not exist.

Supposing that dimming (darkening) is carried out from the state shownin FIG. 4 to the state shown in FIG. 3, there occurs a transition fromthe state where the non-operating period does not exist to the statewhere the non-operating period exists, and therefore, discontinuousluminous flux change occurs. That is, since the non-operating periodabruptly begins upon transition from continuous operation driving tointermittent driving, the brightness is pronouncedly changed. Such adiscontinuous luminous flux change (unevenness of dimming) observed whendarkening is carried out from full illumination does not occur in adimmable incandescent lamp, and thus makes a user feel uncomfortable.

This discontinuous luminous flux change will be further described withreference to FIG. 5. FIG. 5 includes the states shown in FIG. 3 and FIG.4 in the same diagram so as to provide an easy-to-understanddescription. FIG. 5( a) shows a phase-controlled voltage (outputwaveform from the dimmer), FIG. 5( b) shows three kinds of dimmingcommand voltages (i), (ii) and (iii), and a sawtooth wave. Further,FIGS. 5( c), (d) and (e) show the intermittent command signals (ONcommand periods, OFF command periods) and the non-operating periods,corresponding to the dimming command voltages (i), (ii) and (iii).

First, like the dimming command voltage (i), if the dimming commandvoltage (dimming command signal) exceeds the maximum value of thevoltage variation range of the triangular wave, the continuous operatingstate is reached, and thus the intermittent dimmable operating state isnot reached as shown in FIG. 5( c).

Next, like the dimming command voltage (ii), if the dimming commandvoltage becomes equal to the maximum value of the voltage variationrange of the triangular wave, a signal of the OFF command period isoutputted during the ON command period, and the intermittent dimmableoperating state is reached as shown in FIG. 5( d). As shown in FIG. 5(d), even if the OFF command period is short, the lamp enters thenon-operating period (i.e., the non-operating period due to the start ofoperation) during the rise time thereof.

Further, like the dimming command voltage (iii), if the dimming commandvoltage is reduced, not only the OFF command period is extended but alsothe non-operating period is prolonged as shown in FIG. 5( e), resultingin a reduction in luminous flux.

Now, if a transition is made from the state shown in FIG. 5( c) to thatshown in FIG. 5( d), the lamp, which has been in the continuousoperating state thus far, momentarily enters the non-operating period,and therefore, the luminous flux change becomes discontinuous. Asalready mentioned above, this discontinuous luminous flux change is notpreferable because it makes a user feel uncomfortable. On the otherhand, if a transition is made from the state shown in FIG. 5( d) to thatshown in FIG. 5( e), the luminous flux change is continuous because thistransition takes place between both the states where the non-operatingperiods exist; hence, it is possible to eliminate the above-describedproblem that a user feels uncomfortable.

In short, the electrodeless discharge lamp operating device of thepresent embodiment is formed so as to prevent the dimming command signalfrom exceeding the limiter value set lower than the maximum value of thevoltage variation range of the sawtooth wave; therefore, it is possibleto always carry out intermittent driving such that the OFF commandperiod (extinguishing period) exists, and as a result, a discontinuoustime period is prevented from occurring in luminous flux change. Inother words, the dimming controller 7 of the present embodiment outputsa signal for placing the electrodeless discharge lamp 3 into theintermittent dimmable operating state (e.g., the dimming command voltage(ii) or (iii) shown in FIG. 5( b)) even if dimming state is in fullillumination, and does not output a signal for placing the electrodelessdischarge lamp 3 into the continuous operating state (e.g., the dimmingcommand voltage (i) shown in FIG. 5( b)) even if dimming state reachesfull illumination.

In the configuration shown in FIG. 1, the voltage limiter 25 is providedso that the continuous operating state is not reached; however, otherconfiguration may be adopted as long as the intermittent dimmableoperating state can be maintained even if dimming is in fullillumination state.

For example, the dimming controller 7 may be formed such that the angleand time of the sawtooth wave are set by a predetermined circuit, andthe dimming command signal is prevented from exceeding the limiter valueset lower than the maximum value of the voltage variation range of thesawtooth wave. Besides, the configuration of the dimmer 2 may bemodified so that the intermittent dimmable operating state is maintainedeven if the dial or volume of the dimmer 2 is turned to maximum. In thatcase, typically, in consideration of characteristic variations in thedimmer or variations in the sawtooth wave, it is sufficient that theposition of 95% output or 90% output, for example, corresponds to themaximum of the dial or volume of the dimmer 2.

As described above, in the electrodeless discharge lamp operating device(electrodeless self-ballasted fluorescent lamp) of the first embodiment,the dimming controller 7 outputs a signal for maintaining theintermittent dimmable operating state even if dimming is in fullillumination state, and therefore, discontinuous luminous flux changecan be prevented from occurring. As a consequence, a user does not feeluncomfortable. Furthermore, replacement with an incandescent lamp isenabled, and in addition, the electrodeless self-ballasted fluorescentlamp provided with dimming function can be further popularized.

It should be noted that in the present embodiment, the configuration ofthe electrodeless self-ballasted fluorescent lamp has been described;however, the present embodiment may also be applied to an electrodelessself-ballasted discharge lamp having no fluorescent material. In otherwords, the present embodiment may be applied to a discharge lamp such asa lamp for sterilization in which no fluorescent material is applied toits discharge bulb. Furthermore, the application is not limited togeneral illumination but may include, for example, the operation of alamp for emitting rays of light for a person's health, which has anaction spectrum effective against erythema or effective in generatingvitamin D, or a lamp for growing plants, which has an action spectrumeffective in enabling photosynthesis or morphogenesis of plants. Inaddition, as can be understood from the circuit diagram shown in FIG. 1,the configuration of the present embodiment is not limited to aself-ballasted lamp operating device, but may be applied to a dischargelamp operating device (i.e., an electrodeless discharge lamp operatingdevice) in which the electrodeless fluorescent lamp 3 and the ballastcircuit 4 are independently provided.

Hereinafter, a brief description will be made about the frequency of thehigh-frequency voltage applied from the ballast circuit 4 to theelectrodeless fluorescent lamp 3 in the electrodeless self-ballastedfluorescent lamp of the present embodiment. The frequency in the presentembodiment is in a relatively low frequency range of 1 MHz or less(e.g., 50 kHz to 500 kHz) as compared with an ISM frequency band of13.56 MHz or several MHz which is practically and generally utilized.The frequency in such a low frequency range is used because of thefollowing reasons. First, if the lamp is operated in a relatively highfrequency range such as 13.56 MHz or several MHz, a noise filter forsuppressing line noise generated from a high-frequency power supplycircuit within the ballast circuit (circuit board) is increased in size,which undesirably increases the volume of the high-frequency powersupply circuit. Further, supposing that noise radiated or propagatedfrom the lamp is high-frequency noise, since laws and regulations arevery strictly restricting the high-frequency noise, an expensive shieldhas to be provided and utilized in order to meet the restrictions, whichpresents a serious obstacle in achieving cost reduction. To thecontrary, if the lamp is operated in a frequency range of about 1 MHz to50 kHz, inexpensive general-purpose products, which are used aselectronic components for general electronic equipment, can be utilizedas components for forming the high-frequency power supply circuit; inaddition, since the use of small-sized components is enabled, not onlycost reduction but also size reduction can be achieved, thus obtainingconsiderable advantages. It is to be noted that the electrodelessfluorescent lamp 3 of the present embodiment does not have to beoperated at a frequency of 1 MHz or less, but may alternatively beoperated in a frequency range of 13.56 MHz or several MHz, for example.

(Embodiment 2)

Hereinafter, a second embodiment of the present invention will bedescribed with reference to FIG. 6. Although the configuration of adischarge lamp operating device of the present embodiment is similar tothat described in the first embodiment, a sawtooth wave generator 20 fordetecting the turn-on of a phase-controlled voltage is formeddifferently from the counterpart in the first embodiment, and can beformed inexpensively without using any IC in the configuration of thepresent embodiment.

FIG. 6 shows a circuit for detecting the turn-on of a phase-controlledvoltage in the present embodiment, and in particular shows theconfiguration of the sawtooth wave generator 20. It should be noted thatthe same constituting elements as the counterparts described in thefirst embodiment are identified by the same reference characters, andthe further description thereof will be omitted.

The sawtooth wave generator 20 shown in FIG. 6 has: a differentiatingcircuit 201; a diode 202; a transistor 203; and a capacitor 204, and thedifferentiating circuit 201 includes a capacitor and a resistor. Thesawtooth wave generator 20 is connected to a dimming control signalinput section A 18 via a photo coupler 19, the dimming control signalinput section A 18 is connected to a dimmer 2, and the dimmer 2 iselectrically connected to a commercial power supply 1.

In the present embodiment, the differentiating circuit 201 is connectedto a collector terminal of the transistor of the photo coupler 19, whichgenerates a pulse wave synchronized with the turn-on and turn-off of aphase-controlled AC voltage. An output terminal of the differentiatingcircuit 201 is connected with an anode of the diode 202, while a cathodeof the diode 202 is connected with a base terminal of the transistor 203for discharge. Between a collector terminal and an emitter terminal ofthe transistor 203 for discharge, the capacitor 204 for charge anddischarge is connected. Due to such a configuration, the sawtooth wavegenerator 20 can generate a sawtooth wave synchronized with the turn-onof the phase-controlled voltage.

Hereinafter, operations to be performed in the present embodiment willbe briefly described. Note that in the configuration of the presentembodiment, the operation of the discharge lamp is based on the sameprinciple as the first embodiment, and the further description thereofwill be omitted.

Due to the pulse wave from the photo coupler 19, an output signal of thedifferentiating circuit 201 becomes a differential wave synchronizedwith a rising edge and a falling edge of the pulse wave, and only thedifferential wave synchronized with the rising edge by using the diode202 with a low leakage current is inputted to the base terminal of thetransistor 203. And the capacitor 204 connected between the collectorterminal and emitter terminal of the transistor repeats charge anddischarge using, as a trigger, the rising edge of the pulse wave fromthe photo coupler 19, thus allowing the generation of a sawtooth wave.

If the configuration of the second embodiment is adopted, it becomespossible to implement the sawtooth wave generator 20 with inexpensivecomponents without using any expensive IC components. It should be notedthat; more favorably, a buffer circuit is added, thus increasing outputimpedance.

(Embodiment 3)

FIG. 7 is a circuit diagram of a discharge lamp operating deviceaccording to a third embodiment of the present invention. The thirdembodiment differs from the above-described first embodiment in that adischarge bulb 17′ has electrodes, and that a load resonant circuit isdifferently formed for the operation of a fluorescent lamp 3′ havingelectrodes. It should be noted that the same constituting elements asthe counterparts described in the first embodiment are identified by thesame reference characters, and the further description thereof will beomitted.

In the configuration of the present embodiment, as shown in FIG. 7, anLC resonant circuit including: a fluorescent lamp 3′; a resonantinductor 13; a resonant capacitor 15; and a capacitor 14 for resonanceand preheat is connected between a drain terminal and a source terminalof a MOSFET 12.

In the configuration of the present embodiment, if a high voltage isgenerated as a resonance voltage at both ends of the capacitor 14 of theLC resonant circuit, the temperature of each electrode is increased dueto a preheat current flowing to the two electrodes within the dischargebulb 17′, and if the generation of thermion from the electrodes iseasily allowed, the discharge bulb 17′ causes a breakdown and startsdischarge. Once the discharge bulb 17′ has started the discharge, thecurrent flowing through the discharge bulb 17′ is limited by theresonant inductor 15, thus maintaining the stable discharge.

The configuration and operation of a dimming controller 7 of the presentembodiment are similar to those of the dimming controller 7 of the firstembodiment. By implementing the configuration of the discharge lampoperating device as shown in FIG. 7, it becomes possible to stably carryout dimmable operation of the dimmable fluorescent lamp havingelectrodes.

Although the discharge lamp operating device of the present embodimentincludes the fluorescent lamp 3′ having electrodes, the ballast circuit4 for carrying out intermittent driving is more suitable for use incombination with the electrodeless fluorescent lamp 3 of the firstembodiment than for use in combination with the fluorescent lamp 3′having electrodes according to the present embodiment. This is becausesince the intermittent driving is an operation that repeats turning-onand turning-off, the electrodes of the fluorescent lamp 3′ are severelyworn out, thus causing the problem that their lives are shortened. Inthe present invention, since the electrodeless discharge lamp 3 has noelectrode to begin with, such a problem will not occur.

It should be noted that in the first embodiment, the dimming controller7 is formed so as to output a signal for synchronizing the timing of theturn-on of the phase-controlled voltage with that of the operation ofthe lamp intermittently driven by the DC-AC converter 6 because dimmingoperation can be carried out more favorably if the synchronization isachieved.

In the configuration shown in FIG. 8, a ballast circuit 4′ carries outintermittent driving, but is not intended to synchronize the timing ofthe turn-on of the phase-controlled voltage with that of the operationof the lamp intermittently driven by a DC-AC converter 6. Theconfiguration shown in FIG. 7 differs from that of the first embodimentin that a dimming controller 7′ is formed so as to generate a dimmingcontrol signal and send a dimming command signal to the DC-AC converter(inverter circuit) 6.

The dimming controller 7′ is made up of: a dimming signal generator 74;and a dimming command signal section 10 for sending the dimming commandsignal to the DC-AC converter 6. An output from a dimmer 2,phase-controlled by a triac, is half-wave rectified through a half-waverectifier 71, a comparator 73 compares the resulting output voltage (120Hz) with an output voltage from a triangular wave generator 72 forgenerating a reference voltage with a reference frequency (120 Hz), andthen the comparator 73 outputs a pulse shape dimming signal with aconstant frequency. The dimming signal is sent to the DC-AC converter 6via the dimming command signal section 10, and the dimming of theelectrodeless fluorescent lamp 3 is carried out while the on time andoff time of the DC-AC converter 6 being changed. The electrodelessfluorescent lamp 3 is used as a discharge lamp, the switching frequencyf1 of the inverter circuit is 200 kHz, and MOSFETs are used as switchingelements.

FIG. 9 shows experimental results obtained from the configuration shownin FIG. 8. Hereinafter, in addition to the contents shown in FIG. 9, theoperation and characteristic of the discharge lamp operating deviceshown in FIG. 8 will be described.

FIG. 9 illustrates waveform charts showing waveforms a through d, inwhich each horizontal axis is a time axis, and the time axis serves as acommon measure in the respective waveform charts.

In FIG. 9, a represents the waveform of the voltage phase-controlled inthe dimmer 2. As can be seen from this chart, the conduction angle ofthe triac of the dimmer 2 is close to π, and therefore, considerablydeep dimming is carried out. In FIG. 9, b represents the dimming commandsignal that is sent from the dimming controller 7′ to the DC-ACconverter 6 when the phase-controlled voltage such as one having thewaveform a in FIG. 9 is inputted to the ballast circuit 4′.

As can be understood from the comparison made between the waveforms aand b in FIG. 9, the turn-on of the phase-controlled voltage is notsynchronized with the turn-on of the dimming command signal. That is,after the turn-on of the phase-controlled voltage, the sending of thedimming command signal from the dimming controller 7′ to the DC-ACconverter 6 is delayed by a time period Δt. Since a large amount ofenergy is required for the start of operation of the electrodelessfluorescent lamp 3, a large drain current flows through each of theMOSFETs 11 and 12 at the moment of operation of the lamp as indicated bythe waveform c in FIG. 9. If the turn-on of the dimming command signalis delayed from that of the phase-controlled voltage by the time periodΔt, the rising of the drain current of each of the MOSFETs 11 and 12 isdelayed. Thus, a period of time during which a high-frequency electricpower is supplied to the electrodeless fluorescent lamp 3 and a periodof time for light emission are reduced accordingly, and in addition, thedriving of the DC-AC converter 6 is stopped in the state where thephase-controlled voltage right after the turn-on thereof is at a highestlevel; consequently, a reduction in the light emission output of theelectrodeless discharge lamp 3 is significant.

If deeper dimming is carried out using the dimmer 2, the drain currentof each of the MOSFETs 11 and 12 is decreased, and as a result, thehigh-frequency electric power supplied to the electrodeless fluorescentlamp 3 is reduced, and a threshold state where the lamp is operated orextinguished is nearly reached. In other example, there occurs a timelag as shown in FIG. 10. Also in this example, since the synchronizationis not achieved, the high-frequency electric power supplied to theelectrodeless fluorescent lamp 3 is similarly reduced, and the thresholdstate where the lamp is operated or extinguished is nearly reached. Insuch a state, flickering or undesirable extinguishing easily occurs, andfurthermore, in carrying out deep dimming, the electrodeless fluorescentlamp 3 cannot be operated at all if the time lag Δt becomes too long.

The effects of the present invention are obtainable even if such anunstable state exists; however, in order to further extend dimmablerange, it is preferable to achieve the synchronization and reduce thepossibility of reaching the unstable state even if deeper dimming iscarried out. This is because the range in which the actual brightness isvariable (i.e., the range of the actual dimming) can be extendedaccordingly in that case, and as a result, a more outstanding dimmableelectrodeless discharge lamp can be implemented.

According to the present invention, since the dimming controller outputsa signal for maintaining the intermittent dimmable operating state evenif dimming state is in full illumination, it becomes possible to preventdiscontinuous luminous flux change from occurring, and as a consequence,it becomes possible to make a user feel less uncomfortable.

INDUSTRIAL APPLICABILITY

In the present invention, it is possible to output a signal formaintaining an intermittent dimmable operating state even if dimmingstate is in full illumination so that the occurrence of discontinuousluminous flux change is prevented, and therefore, it is possible toprovide an electrodeless discharge lamp that can be dimmed withoutcausing uncomfortableness, resulting in an excellent industrialapplicability.

1. An electrodeless discharge lamp operating device comprising: an electrodeless discharge lamp; and a ballast circuit for applying a high-frequency voltage to the electrodeless discharge lamp, wherein the ballast circuit comprises: an AC-DC converter for converting a phase-controlled AC voltage into a DC voltage; a DC-AC converter for converting the DC voltage into a high-frequency voltage, the DC-AC converter being formed so as to intermittently drive the electrodeless discharge lamp due to the existence of an operating period during which the high-frequency voltage is applied to the electrodeless discharge lamp so that the electrodeless discharge lamp is operated, and an extinguishing period during which the generation of the high-frequency voltage is stopped so that the electrodeless discharge lamp is extinguished; and a dimming controller for detecting the turn-on of the phase-controlled AC voltage, for outputting an intermittent command signal that changes the ratio between the operating period and the extinguishing period to the DC-AC converter, and for outputting a signal that maintains an intermittent dimmable operating state even if dimming is in full illumination state.
 2. An electrodeless discharge lamp operating device comprising: an electrodeless discharge lamp; and a ballast circuit for applying a high-frequency voltage to the electrodeless discharge lamp, wherein the ballast circuit comprises: an AC-DC converter for converting a phase-controlled AC voltage into a DC voltage; a DC-AC converter for converting the DC voltage into a high-frequency voltage; and a dimming controller for outputting an intermittent driving signal to the DC-AC converter, wherein the dimming controller comprises: a circuit for generating a sawtooth wave or a triangular wave synchronized with the turn-on of the phase-controlled AC voltage; and a dimming command signal generator for generating a dimming command signal, and wherein the dimming controller is formed so as to prevent the dimming command signal from exceeding a limiter value set lower than the maximum value of the voltage variation range of the sawtooth wave or the triangular wave.
 3. The electrodeless discharge lamp operating device of claim 2, wherein the dimming controller has a voltage limiter, which is connected to the dimming command signal generator, for preventing the dimming command signal from exceeding the limiter value.
 4. The electrodeless discharge lamp operating device of claim 2, wherein the dimming controller is further formed so as to output a signal for synchronizing the timing of the turn-on with that of the operation of the lamp intermittently driven by the DC-AC converter.
 5. An electrodeless discharge lamp operating device comprising: an electrodeless discharge lamp; and a ballast circuit for applying a high-frequency voltage to the electrodeless discharge lamp, wherein the ballast circuit comprises: an AC-DC converter for converting a phase-controlled AC voltage into a DC voltage; a DC-AC converter for converting the DC voltage into a high-frequency voltage and for intermittently driving the electrodeless discharge lamp; and a dimming controller for detecting the turn-on of the phase-controlled AC voltage and for outputting an intermittent command signal that changes the ratio between an operating period and an extinguishing period to the DC-AC converter, and wherein the dimming controller comprises: a circuit for generating a sawtooth wave or a triangular wave responsive to the turn-on phase of the waveform of the phase-controlled voltage; a dimming command signal generator for generating a dimming command signal responsive to the turn-on phase of the waveform of the phase-controlled voltage; a comparator for comparing the voltage of the sawtooth wave or the triangular wave with that of the dimming command signal and for outputting the intermittent command signal; and a voltage limiter provided between the comparator and the dimming command signal generator.
 6. The electrodeless discharge lamp operating device of claim 5, wherein the dimming controller does not output a signal for placing the electrodeless discharge lamp into a continuous operating state even if dimming state reaches full illumination, and outputs a signal for placing the electrodeless discharge lamp into an intermittent dimmable operating state even if dimming state is in full illumination.
 7. The electrodeless discharge lamp operating device of claim 1, wherein the dimming controller has a sawtooth wave generator comprising a differentiating circuit that comprises a capacitor and a resistor, wherein the differentiating circuit is connected to a collector terminal of a transistor for generating a pulse wave synchronized with the turn-on and turn-off of the phase-controlled AC voltage, wherein an output terminal of the differentiating circuit is connected with an anode of a diode, while a cathode of the diode is connected with a base terminal of a transistor for discharge, and wherein a capacitor for charge and discharge is connected between a collector terminal and an emitter terminal of the transistor for discharge, thus allowing the generation of a sawtooth wave synchronized with the turn-on of the phase-controlled AC voltage.
 8. The electrodeless discharge lamp operating device of claim 1, wherein the phase-controlled AC voltage is an output voltage of a dimmer which has been phase-controlled by the dimmer.
 9. An electrodeless self-ballasted fluorescent lamp comprising: an electrodeless fluorescent lamp; a ballast circuit for applying a high-frequency voltage to the electrodeless fluorescent lamp; and a lamp base electrically connected to the ballast circuit, wherein the electrodeless fluorescent lamp, the ballast circuit and the lamp base are formed as one unit, wherein the ballast circuit comprises: an AC-DC converter for converting a phase-controlled AC voltage into a DC voltage; a DC-AC converter for converting the DC voltage into a high-frequency voltage, the DC-AC converter being formed so as to intermittently drive the electrodeless fluorescent lamp due to the existence of an operating period during which the high-frequency voltage is applied to the electrodeless fluorescent lamp so that the electrodeless fluorescent lamp is operated, and an extinguishing period during which the generation of the high-frequency voltage is stopped so that the electrodeless fluorescent lamp is extinguished; and a dimming controller for detecting the turn-on of the phase-controlled AC voltage, for outputting an intermittent command signal that changes the ratio between the operating period and the extinguishing period to the DC-AC converter, and for outputting a signal that maintains an intermittent dimmable operating state even if dimming is in full illumination state.
 10. A discharge lamp operating device comprising: a discharge lamp; an AC-DC converter for converting a phase-controlled AC voltage into a DC voltage; a DC-AC converter for converting the DC voltage into a high-frequency voltage, the DC-AC converter intermittently driving the discharge lamp due to the existence of an operating period during which the high-frequency voltage is applied to the discharge lamp so that the discharge lamp is operated, and an extinguishing period during which the generation of the high-frequency voltage is stopped so that the discharge lamp is extinguished; and a dimming controller for detecting the turn-on of the phase-controlled AC voltage, for outputting an intermittent command signal that changes the ratio between the operating period and the extinguishing period to the DC-AC converter, and for outputting a signal that maintains an intermittent dimmable operating state even if dimming is in full illumination state.
 11. The discharge lamp operating device of claim 10, wherein the dimming controller is further formed so as to output a signal for synchronizing the timing of the turn-on with that of the operation of the lamp intermittently driven by the DC-AC converter.
 12. The discharge lamp operating device of claim 10, wherein the discharge lamp has a discharge bulb having a recessed portion, and wherein an induction coil is inserted into the recessed portion of the discharge bulb.
 13. The electrodeless discharge lamp operating device of claim 2, wherein the phase-controlled AC voltage is an output voltage of a dimmer which has been phase-controlled by the dimmer.
 14. The electrodeless discharge lamp operating device of claim 5, wherein the phase-controlled AC voltage is an output voltage of a dimmer which has been phase-controlled by the dimmer. 